Parts of the guitar

• 1. Headstock
• 2. Nut
• 3. Machine heads (or pegheads, tuning keys, tuning machines, tuners)
• 4. Fretwires
• 5. Truss rod (not shown)
• 6. Inlays
• 7. Neck and fretboard
• 8. Heel (acoustic or Spanish)- Neckjoint (electric)
• 9. Body
• 10. Pickups (not applicable to classical guitars)
• 11. Electronics (not applicable to classical guitars)
• 12. Bridge (saddle)
• 13. Pickguard
• 14. Bottom deck
• 15. Soundboard (=top deck)
• 16. Body sides
• 17. Sound hole, with Rosette inlay
• 18. Strings
• 19. Bridge

Headstock

The headstock is located at the end of the guitar neck furthest from the body. It is fitted with machine heads that adjust the tension of the strings, which in turn affects the pitch. Traditional tuner layout is "3+3" in which each side of the headstock has three tuners. In this layout, the headstocks are commonly symmetrical. Some guitars feature other layouts as well, including six-in-line.

Nut

The nut is a small strip of bone, plastic, brass, graphite, corian, or other medium-hard material, at the joint where the headstock meets the fretboard. Its grooves guide the strings onto the fretboard, giving consistent lateral string placement. It is one of the endpoints of the strings' vibrating length. It must be accurately cut, or it can contribute to tuning problems due to string slippage, and/or string buzz.

Fretboard

Also called the fingerboard is a piece of wood embedded with metal fretwires that comprises the top of the neck. It is flat or slightly curved. The curvature of the fretboard is measured by the fretboard radius, which is the radius of a hypothetical circle of which the fretboard's surface constitutes a segment. The smaller the fretboard radius, the more noticeably curved the fretboard is. Pinching a string against the fretboard effectively shortens the vibrating length of the string, producing a higher tone (a string, unfingered, will vibrate from the saddle to the nut; once fingered, it will vibrate only along the distance between the saddle and the fretwire directly before the finger). Fretboards are most commonly made of ebony.

Frets

Frets are the spaces between the fretwires which are the metal strips (usually nickel alloy or stainless steel) embedded along the fretboard placed in points along the length of string that divide it mathematically. When strings are pressed down behind them, fretwires shorten the strings' vibrating lengths to produce different pitches- each one spaced a half-step apart on the 12 tone scale. For more on fret spacing, see the Strings and Tuning section below. Fretwires are usually the first permanent part to wear out on a heavily played guitar. They can be re-shaped to a certain extent and can be replaced as needed. Frets also indicate fractions of the length of a string (the string midpoint is at the 12th fret; one-third the length of the string reaches from the nut to the 7th fret, the 7th fret to the 19th, and the 19th to the saddle; one-quarter reaches from nut to fifth to twelfth to twenty-fourth to saddle). This feature is important in playing harmonics. Frets are available in several different gauges, depending on the type of guitar and the player's style.

Guitars have frets on the fingerboard to fix the positions of notes and scales, which gives them equal temperament. Consequently, the ratio of the widths of two consecutive frets is the twelfth root of two , whose numeric value is about 1.059463. The twelfth fret divides the string in two exact halves and the 24th fret (if present) divides the string in half yet again. Every twelve frets represents one octave.

There are several styles of fret, which allow different sounds and techniques to be exploited by the player.

Truss rod

The truss rod is an adjustable metal rod that runs along the inside of the neck, adjusted by a hex nut or an allen-key bolt usually located either at the headstock (under a cover) or just inside the body of the guitar, underneath the fretboard (accessible through the sound hole). Most classical guitars do not have truss rods, as the nylon strings do not put enough tension on the neck for one to be needed. The truss rod counteracts the immense amount of tension the strings place on the neck, bringing the neck back to a straighter position. The truss rod can be adjusted to compensate for changes in the neck wood due to changes in humidity or to compensate for changes in the tension of strings. Tightening the rod will curve the neck back and loosening it will return it forward. Adjusting the truss rod affects the intonation of a guitar as well as affecting the action (the height of the strings from the fingerboard). Some truss rod systems, called "double action" truss systems, will tighten both ways, allowing the neck to be pushed both forward and backward (most truss rods can only be loosened so much, beyond which the bolt will just come loose and the neck will no longer be pulled backward).

Neck

A classical guitar's frets, fretboard, tuners, headstock, and truss rod, all attached to a long wooden extension, collectively comprise its neck. The wood used to make the fretboard will usually differ from the wood in the rest of the neck. The bending stress on the neck is considerable, particularly when heavier gauge strings are used (see Strings and tuning), and the ability of the neck to resist bending (see Truss rod) is important to the guitar's ability to hold a constant pitch during tuning or when strings are fretted. The rigidity of the neck with respect to the body of the guitar is one determinant of a good instrument versus a poor one. The shape of the neck can also vary, from a gentle "C" curve to a more pronounced "V" curve.

Neck joint or 'Heel'

This is the point at which the neck is either bolted or glued to the body of the guitar. Almost all acoustic guitars, with the primary exception of Taylors, and Greg Smalmann have glued (otherwise known as set) necks.

On Classical guitars, this portion is known as the 'heel' because it looks like a Spanish type shoe heel. Set necks usually feature dovetail joints, which offer stability and sustain. Other commonly used neck joints include mortise-and-tenon joints (such as those used by CF Martin & Co. guitars), and Classical heel style neck joints (commonly found in classical guitars). Bolt-on necks, though they are historically associated with cheaper instruments, do offer greater flexibility in the guitar's set-up, and allow easier access for neck joint maintenance and repairs.

Body

The body of the instrument is a major determinant of the overall sound variety for acoustic guitars. The guitar top, or soundboard, is a finely crafted and engineered element often made of spruce, red cedar or mahogany. This thin (often 2 or 3 mm thick) piece of wood, strengthened by different types of internal bracing, is considered to be the most prominent factor in determining the sound quality of a guitar. The majority of the sound is caused by vibration of the guitar top as the energy of the vibrating strings is transferred to it. Different patterns of wood bracing have been used through the years by luthiers (Torres, Hauser, Ramirez, Fleta, and C.F. Martin being among the most influential designers of their times); to not only strengthen the top against collapsing under the tremendous stress exerted by the tensioned strings, but also to affect the resonation of the top. The back and sides are made out of a variety of woods such as mahogany, Indian rosewood and highly regarded Brazilian rosewood (Dalbergia nigra). Each one is chosen for their aesthetic effect and structural strength, and can also play a significant role in determining the instrument's timbre. These are also strengthened with internal bracing, and decorated with inlays and purfling.

The body of an classical guitar is a resonating chamber which projects the vibrations of the body through a sound hole, allowing the acoustic guitar to be heard without amplification. The sound hole is normally a round hole in the top of the guitar (under the strings), though some may have different placement, shapes or multiple holes.

As an instrument's maximum volume is determined by how much air it can move.

Binding, Purfling, and Kerfing

The top, back and rim of a classical guitar body are very thin (1-2 mm), so a flexible piece of wood called kerfing (because it is often scored, or kerfed to allow it to bend with the shape of the rim) is glued into the corners where the rim meets the top and back. This interior reinforcement provides 5 to 20 mm or solid gluing area for these corner joints.

During final construction, a small section of the outside corners is carved or routed out and then filled binding material on the oustide corners and decorative strips of material next to the binding, which are called purfling. This binding serves to seal off the endgrain of the top and back. Binding and purfling materials are generally made of either wood or high quality plastic materials.

Bridge

The main purpose of the bridge on a classical guitar is to transfer the vibration from the strings to the soundboard, which vibrates the air inside of the guitar, thereby amplifying the sound produced by the strings. The bridge holds the strings in place on the body.